1. Technical Field
The present invention relates generally to computer networks and, in particular, to a novel transcoding framework that includes one or more transcoder sub-chains.
2. Description of the Related Art
Intermediaries are computational entities that can be positioned anywhere along a data stream, e.g., an HTTP stream, and are programmed to tailor, customize, personalize, or otherwise distill or enhance data as it flows along the stream. A caching web proxy is a simple example of an HTTP intermediary. Intermediary-based programming is particularly useful for adding functionality to a system when the data producer (e.g., a server or database) or the data consumer (e.g., a browser) cannot be modified.
A known intermediary architecture and framework, called Web Intermediaries (or WBI, pronounced xe2x80x9cwebbyxe2x80x9d), is useful for creating intermediary applications on the web. Basically, WBI is a programmable web proxy and web server that, together with a web development kit, may be used with Java APIs for building web intermediary applications within the WBI framework. Examples of intermediary applications include: transcoding content between formats, personalization, password and privacy management, interactivity, and content filtering. WBI is just one example of an architecture for managing web intermediaries. Other conceptual techniques include, for example, chaining of Java servlets.
A transcoder is a functional module, typically in the form of a piece of computer code, that accepts a data stream as input and produces a data stream as output. The output stream is created based on the transcoder""s input stream and the function that the transcoder is designed to perform. This function could be one of any number of operations such as: a monitoring activity for which information is collected before passing the input stream on as output, an editing operation where incoming data is modified in some way before it is output, or a data generation operation, where incoming data is treated as a request for more data available either inside or outside the system, which is then passed on as output from the transcoder. A given transcoder output stream may also be based upon an original or modified request, histographical information on transcoding paths already taken, and/or external preferences (e.g., network connection speed, client device capabilities, user preferences, and the like) established in a separate database. A given transcoder may have a proprietary interface to obtain these preferences, or it may use XSL style sheets to apply such preferences.
The use of streams to service the input and output needs of a transcoder is the implementation used by the WBI model. Transcoders, however, may also operate on data in a system organized, for example, according to a Document Object Model (DOM), via a reference to that model.
A set of xe2x80x9cnxe2x80x9d transcoders may be used together to provide more complex transcoding operations in a rule driven fashion. For example, as an input stream proceeds through the network, various transcoders may modify that stream, acquire data from an external source (e.g., an origin web server) and subsequently modify that data stream before returning the final output stream (the response). Such a framework works well when the operation to be performed is homogeneous and xe2x80x9cflatxe2x80x9d in nature.
If, however, the transcoding operations are hierarchical or require compound repetitive operations, the above-described functionality may be inefficient when performed monolithically. A monolithic operation is one that is performed in whole by a given transcoder. When hierarchical or compound repetitive operations are required, the use of monolithic transcoding operations has the effect of making some of the transcoders in the chain excessively complex. For example, a given transcoder may have to perform multiple operations to acquire, aggregate and post-process some external data prior to passing its output stream on to another transcoder.
The present invention addresses this problem.
It is a primary object of the present invention to provide a transcoding framework that is modular. Preferably, a given transcoder in the framework need not be a monolithic implementation that contains all of the functionality needed to perform a complete task.
It is another primary object of the invention to provide a novel transcoding framework wherein sub-chained transcoders are used as modules to provide various reentrant transcoding functions that may be shared across the framework.
It is still another object of the present invention to sub-chain transcoders within the framework to flatten a non-homogeneous data stream possessing hierarchical components, thereby decreasing composition time and providing faster delivery of documents to the requester.
Still another object of this invention is to provide a transcoding framework that supports recursive use of given-sub-chained transcoders.
A still further object of this invention is to service a given request (e.g., HTTP, WML, FTP, or the like) using a transcoder in a chain that has the capability of creating subchains of known transcoders to assist in flattening a document comprised of multiple resources into a single format for the next transcoder in the chain (or the end requester if the end of the chain has been reached).
Another more general object of this invention is to enable a given transcoder in a chain to use a sub-chain of transcoders one or more times to assist in completing the given transcoder""s operation as similar external resources are encountered. These subchains may be asked to process these resources in parallel and to notify the given transcoder when they have finished processed their assigned resource.
Yet another more general object of this invention is to provide a transcoding framework that takes advantage of subsets of transcoders as reusable components that can be used multiple times to retrieve external data parts while processing a particular request.
A further feature of the invention is the use of transcoder subchains in parallel for providing performance gains.
These and other objects and features are provided by a novel transcoding framework of the present invention. A given transcoder in the framework comprises a transcoding function (e.g., a generator, an editor, a monitor, or the like), a data structure for identifying one or more sub-chains of specialized transcoders that are available to the transcoder, and a control routine. In one embodiment, the routine is responsive to recognition of an external reference that cannot be transcoded by the transcoding function (a) for locating a sub-chain of specialized transcoders in the data structure, (b) for calling the sub-chain of specialized transcoders, (c) for receiving a transcoded external reference provided by the sub-chain of specialized transcoders, and (d) for incorporating the transcoded external reference in an output of the transcoder.
According to another feature of the present invention, a method is provided for transcoding an input stream to a desired output format using a transcoder framework. In response to a given transcoder of the framework recognizing an external reference that it cannot transcode, the method calls a subseries of specialized transcoders to transcode the external reference. After the subseries of specialized transcoders generates a transcoded external reference, that reference is returned back to the given transcoder, where it is incorporated into the transcoder""s output. Transcoder sub-chains are used in this manner as modular, building blocks in the transcoder framework.
The foregoing has outlined some of the more pertinent objects and features of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention as will be described. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the following Detailed Description of the Preferred Embodiment.